Legitimate authority requires consent, not mere force

Rousseau opens by rejecting the idea that might makes right — that a conqueror's power to compel obedience creates any genuine obligation to obey. Force alone, he argues, produces submission, not legitimate authority; the moment resistance becomes possible, a purely coercive relationship has no moral claim on continued compliance.

He similarly dismisses arguments from tradition or divine right as sufficient justifications for political power, since simply having held power for a long time, or claiming a sacred mandate, doesn't establish that subjects have genuinely agreed to be governed. Legitimacy, for Rousseau, can only come from some form of consent.

This sets up his entire project: if force and tradition can't justify political authority, some other foundation must be found, and he spends the rest of the book constructing that foundation in the form of a contract freely entered into by equals. The through-line is a demand that political power justify itself to those subject to it, rather than simply asserting its own right to exist.